Burner sequence programmer

ABSTRACT

The burner sequence programmer disclosed herein employs an electromechanical switching assembly in which a bi-metal actuator is selectively energized so as to proceed through a sequence of states in which a plurality of contacts are operated in respective predetermined combinations. The contacts control associated circuitry which provide fuel flow control, a spark impulse generation and electrical flame testing, the actuator being energized to proceed to a stable condition in which fuel flow is maintained and spark generation is terminated if ignition is satisfactorily obtained.

United States Patent 1 1 Walbridge 1 Nov. 6, 1973 [54] BURNER SEQUENCE PROGRAMMER [75] Inventor: Lyman l-l. Walbridge, Ashland,

Mass.

[73] Assignee: Walter Kiddie & Company, Inc.,

Clifton, NJ. I

22 Filed: Dec. 20, 1911' 21 Appl. No.: 209,685

52 us. (:1. 431/78 [51] Int. Cl. F23m 5/04 [58] Field of Search 431/78, 18; 236/ll [56] References Cited I i UNITED STATES PATENTS 3,472,220 10/1969 Willson 431/.78 x 3,101,897 8/1963 Vaughn 236/] Primary Examiner-Edward G. Favors Attorney.lohn E. Toupal 57 ABSTRACT terminated if ignition is satisfactorily obtained.

27 Claims 2 Drawing Figures PATENTEUuuv 6 191a INVENTOR.

ATTORNEY.

[man HMMrzt/ge BURNER SEQUENCE PROGRAMMER BACKGROUND OF THE INVENTION cated systems employing expensive timers or stepping switches and relays.

Among the several objects of the present invention may be noted the provision of a burner sequence programmer which provides automatic spark generation Y and flame sensing; the provision of such apparatus which will automatically provide at least one attempt at obtaining reignition; the provision of such a system which will automatically terminate the generation of spark generating impulses when ignition is obtained; the provision of such a system which will proceed to a stable state if ignition is satisfactorily obtained; the provision of such a system which will proceed to a final lock-out state, e.g. necessitating manual resetting, if there is a component failure which requires service at the burner; the provision of such apparatus which is highly reliable; and the provision of such apparatus which is relatively simple and inexpensive. Other objects and features will be in part apparent and in part pointed out hereinafter.

SUMMARY OF THE INVENTION Briefly, apparatus according to the present invention operates to program the sequence of operations of a burner, e.g. such as the burner employed in a domestic I stove broiler, the burner being provided with fuel means which includes a plurality of contacts and an electrically energizable actuator. The actuator, when energized, proceeds progressively through a succession of predetermined states with corresponding contacts being operated in each state. When the actuator is deenergized, it .returns back through the previous states to its initial state. A first circuit is responsive to the operation of the contacts in the initial state of the actuator for energizing the actuator, the actuator being deenergized thereby when a second predeterminedstate is entered. An ignition circuit responds to the operation of the contacts in the-second or ignition state to open the fuel valve and to generate spark-producingimpulses adjacent the burner. A sensing circuit is provided which is responsive only to the presence of a flame at the burner for energizing the actuatorindependently of the first circuit means. If ignition is not obtained, the de-ene-rgized actuator moves to a standby state requiring a momentary loss of power to again try for ignition. However, if a flame is satisfactorily produced, the actuator proceeds to a further, intermediate state in which fuel flow is maintained. Generation of spark-producing impulses is terminated in the intermediate state which preferably'consitutes both a first intermediate state in which the actuator ie energized and a second intermediate state in which the actuator is deenergized. Accordingly, the actuator alternates between these states at some nominal average level of energization. In the event of certain circuit failures the actuator becomes continuously energized and automatically moves to a final or lock-out state requiring manual reset.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic circuit diagram of programming apparatus of the present invention, together with an associated burner construction diagrammatically illustrated;

FIG. 2 illustrates actuator 31 in an unbiased position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, a gas burner of essentially conventional construction is indicated at 11. Burner 11 may, for example, comprise the broiler burner of a conventional domestic cooking stove or other similar appliance burner. Fuel, e. g. natural gas, is supplied to the burner through a solenoid operated valve 13, the solenoid winding being indicated at 15. Mounted adjacent burner 11 are a pair of electrodes 17 and 19 which, as explained hereinafter, function as both spark-generating electrodes and also as a flamesensing means. For this latter purpose, at least one of the electrodes is preferably mounted relative to burner 11 so as to be immersed in the ionized gases which are generated when a flame is present at the burner.

'The electrodes 17 and 19 are connected to the secondary winding W1 of a spark transformer T1. Spark transformer T1 also includes a primary winding W2 which is interconnected with a spark impulse generating circuit. One end of winding W2 is connected,

' through an energy storage capacitor C1, to a lead 21.

With regard to the spark impulse generating circuitry, the lead 21 may be considered to be the common or reference potential. Winding W2 and capacitor C1 together are shuntedby a SCR (Silicon Controlled Rectifier) Q1, the anode of the SCR being connected to the remaining end of winding W2 through 'a diode D1 which is shunted by a resistor R1. During the sparkgenerating mode of operation of the system, capacitor C1 is provided with charging current through a diode D2 which charges this capacitor through resistor R1 and the transformer primary winding, the rate of charging being determined by resistor R1. The charging takes place over a number of am. supply cycles in the spark-generating mode of operation. When the SCR Q1 is then fired, the energy stored on capacitor C1 is discharged by the SCR, through diode D1, into the primary winding of transformer T1 so as to generate a spark impulse at the electrodes 17 and 19 in conventional manner. A timed pulse signal for triggering the SCR is obtained by means of a relaxation oscillator comprising a neon glow tube NEl, which functions as a voltage breakdown device, a timing capacitor C2, and a charging resistor R2. Capacitor C2 is charged from the potential stored on capacitor C1 through resistor R2. Thus, when the voltage on capacitor C2 reaches the breakdown potential of neon glow tube NEl, that tube conducts and generates a pulse signal across the SCR gate resistor R4 thereby triggering the SCR abruptly into conduction. As the current for charging capacitor C2 is taken from across capacitor C1, it will be seen that the SCR cannot be triggered until a sufficient charge to generate a sparking impulse is built up across the energy storage capacitor C1.

As is understood in the art, an electrode mounted adjacent a burner can provide a flame-sensing function in that the ionized gases present in the flame will rectify an a.c. voltage present on the electrode. In the drawing, this rectification function is represented by a diode, designated D8, which is connected between the electrode l9 and the burner 11. The burner is assumed to be grounded as indicated at 22. In the apparatus illustrated, an a.c. voltage which is at certain times present at the gate of SCR O1 is coupled to the electrode 17 through a capacitor C3 opposite the SCR gate. This d.c. component is filtered by means of a resistor R6 and a capacitor C4 and is applied to the cathode of a complementary SCR Q2. As'is understood, the complementary SCR is schematically shown in the same manner as a programmable unijunction transistor (PUT) which can generally be used as a replacement for a complementarySCR; In the present circuit, the complementary SCR performs the function of periodically dumping an accumulated signal, if present, into the gate circuit of the SCR Q1. The gate of the complementary SCR Q2 is connected directly to the cathode of SCR Q1 while its anode is connected thereto through a capacitor C5 which is shunted by a diode D3. Current for turning on the SCR Q2 is provided by the power line through the resistor R8. Capacitor C5 causes this current to lag the line voltage slightly as discussed further hereinafter. I

In providing the sequence of operations desired, the circuitry thus far described operates in conjunction with a switching assembly employing a bi-metal element. In the drawing, this switching assembly is indicated generally at 30, with a bi-metal leaf actuator 31 and a plurality of flexible conductor leafs 33, 34, 35, 36 and 37 having ends mounted in an insulator block 40. A resistance heater for the bi-metal element is indicated at RH. While a-separate heater is illustrated, it may be understood that under certain circumstances integral heating might also be employed. If desired, bimetal element 31 may be compensated for ambient temperature variations in conventional manner.

Bi-metal element 31 is shaped so that, at normal or ambient temperature, this actuator element is in its right hand position, i.e. as illustrated. The actuator itself carries a contact 42, which, in this right hand position, engages and biases slightly to the right contact 43 on flexible conductor leaf 33. Heating of the bi-metal actuator 31 causes it to flex or swing to the left, leaving the fixed contact 43 of leaf 33 after its spring bias is eliminated by a small initial movement. As the actuator contact 42 moves to the left, a series of contacts 44-47 are successively engaged, these latter contacts being mounted, respectively, on the leaf-spring support conductors 34-37 so that as each contact is engaged it can itself move to the left so as to pick up any further contacts in the series. Since the bi-metal element 31, together with its associated heater RH, inherently possesses a finite thermal inertia, it will be understood that the successive contacts will be picked up progressively in a timed sequence. Each contact picked up becomes electrically connected to the actuator contact 42, though this connection may be established through several intermediate contacts. As the successive contacts 7 are picked up, the switching device may be considered as passing through a series of successive states, the contacts being interconnected in predetermined combinations corresponding to the successive states.

The positioning of the first contact 44 is such that it is not engaged immediately after the actuator contact 42 leaves the fixed contact 43. However, as will be understood, retained thermal energy in the heater RH will cause some motion overshoot of the actuator 31 after the heater RH is de-energized. The magnitude of overshoot is, of course, dependent upon the level of thermal energy retained by the heater RH. In the case of startup, the thermal energy accumulated by the heater RH during the period required for the actuator 31 to break the contacts 42 and 43 produces an overshoot that insures engagement of contacts 42 and 44. Conversely, when the actuator is cooling and moves to the right to engage the unbiased leaf spring 33, a shortened heating period is required to move the actuator out of engagement with the leaf spring 33. The correspondingly reduced level of thermal energy accumulation in the heater RH and resultant smaller overshoot of the actuator 31 is insufficient to produce engagement between contacts 42 and 44. Thus, upon cool-down of the actuator 31 automatic recycling will not occur. The importance of this willbe described in greater detail below.

While other types of contact arrangements may be utilized in which various connections are made and/or broken in predetermined sequence, the arrangement illustrated has the advantage that mechanical movement may be coupled through the successive contact leaves which are then also in electrical contact. Thus, insulating motion couplers or spacers, other than at the fixed ends of the leaf-spring supports, are not needed.

A pair of supply leads L1 and L2 provide a.c. power at conventional domestic potentials, e.g. 1 15 volts a.c. at 60 Hz. It is assumed lead L1 is the neutral or grounded lead as indicated. Lead L2 is connected, through a main ON/OFF switch S1 and a fuse F1, to the bi-metal actuator 31 and its contact 42. The switch 81 may, for example, be a thermostatic temperature control switch.

The fixed contact 43, which is engaged by the supply contact 42 when the actuator 31 is cool, is connected to supply current to the spark pulse-generating circuit through the diode D2 and also to one side of the actuator heater RH. The other side of the heater is connected, through a dropping resistor R9, to the common lead L1. Contact 44 is connected to the lead 21 which, as noted previously, constitutes the common lead for the spark-generating ignition circuitry. Contact 44 is also connected, through a diode D5, to the fuel valve solenoid winding 15. This winding is shunted by a further diode D6 which absorbs the inductive surge in conventional manner. Contact 45 is connected, through a bleed resistorR 10, to the timing capacitor C2, which contact 36 is connected to the cathode of the complementary SCR Q2. The last contact in the sequence 47 is connected, through a resistor R l l, to the common lead L1. Resistor R 11 is of relatively low value for purposes described hereinafter.

The operation of this circuit is substantially as follows. When the switch S1 is initially closed, the heater RH is directly energized through the engagement existing between contacts 42 and 43. This is the initial state of the switching assembly. Though contact 43 is connected to diode D2, energization of the sparkgenerating circuitry is prevented by the blocking action provided by diode D5 which also prevents energization of the fuel valve solenoid winding 15.

As the bi-metal heats and moves its contact 42 to the left, it disengages the contact 33 but, as noted above, overshoot produces engagement with the contact 44. In this second or ignition state, the solenoid winding is energized, through the diode D5, during those half cycles in which the lead L2 is negative with respect to lead L1. During those same half cycles, current is provided, through the diode D2, the heater RH, and the resistor R9, to the spark pulse-generating circuit. This circuit is thus energized to generate igniting sparks, as described previously,'between the electrodes 17 and 19. While the spark-generating circuitry draws a slight current load through the" heater RH, this current is not sufficient to prevent the bi-metal actuator from cooling. Thus if satisfactory ignition is not obtained within the delay provided by the thermal inertia and overshoot of the bi-metal element 31, the actuator 31 will begin to cool and move back toward the contact 43 which is in the unbiased position shown in FIG. 2. Immediately upon engagement between contacts 42 and 43, current flow begins in the heater RH to again initiate heating of the bi-metal actuator 31 which, accordingly, reverses itsdirection of movement. The time required to break contacts 42 and 43, however, is substantially less than upon original start-up because of the unbiased po-' sition of the leaf 33. For this reason, less thermal energy is accumulated by the heater RH resulting in a smaller overshoot of the actuator 31 which does not reach the contact 44. The actuator therefore again cools returning toward the contact 43. This cycling operation provides a standby state which continues until the switch S1 is opened to allow further cooling of the actuator 31 and a further return of the leaf 33 toward the biased position in FIG. 1. With the actuator 31 in a biased position and 'upon subsequent I closure of switch 8-1, the system will again try for ignition as described above. It will be-obvious that the switch S1 could be located at a central control panelor that the standby state will be terminated in" the same manner by anytemporary lossof power on line L2. Thus, additional tries for ignition after an initial failure can be instituted withoutmanual reset at the burner.v

If, on the other hand, ignition is obtained while the switching assembly is in its ignition state, i.e., with the contact 42 still in engagement with the contact 44, the presence of flame-generated ions around the electrode 17 will cause a rectification of the a.c. voltage coupled thereto from the gate-cathode circuit of SCR Q1. It should be noted that, although the lead 21 is common with respect to the spark-generating circuitry, it is, in fact, connected to the ungrounded a.c. supply lead L2 through the contact 44. During those a.c. half cycles when the lead L2 is positive with respect to ground, the capacitors C3 and C4 are charged by the flame rectification so that the cathode of the complementary SCR Q2 becomes negative with respect to the cathode of the main SCR Q1. Accordingly, on the alternate a.c. half cycles, when the input junction of the complementary SCR is forwarded biased by positive current flow through resistor R8 into capacitor C5, the complementary SCR will fire, discharging the capacitor C4 into the gate circuit SCR Q1, causing it to conduct. In this mode of operation, SCR Q1 is triggered during each cycle of the applied a.c. power voltage. Accordingly, capacitor C1 does not have a chance to build up a significant charge between firings and the generation of sparks is inhibited by this circuit which responds to the presence of a flame at the burner.

The firing of SCR Q1 during each cycle likewise causes a relatively substantial current to be drawn through the heater RH. Thus, this heater is effectively re-energized once a flame is established at the burner. When the heater is re -energized in this manner, i.e. independently of the path through the fixed contact 33 which is available only in the first or standby state of the switching assembly, the switching device can proceed from its second predetermined state to the next, i.e. an unstable intermediate state that constitutes oscillation between first and second intermediate states. The first intermediate state is produced when engagement takes place between the contact 44 and the contact 45. The connection established by contact 45 shunts the storage capacitor C1 so that the generation of sparking impulses is even more positively inhibited. The bi-metal heater RH, however, continues'to be energized in this state, through the SCR Q1. This continued heating of the bi-metal actuator 31 causes the switching assembly to progress further to the second intermediate state in which the contact 46 is picked up.

Engagement with contact 46 shorts the cathode of the complementary SCR Q2 to the cathode of the main SCR Q1. Accordingly, triggering of the SCR Q1 by the complementary SCR Q2 isinhibited so that the actuator heater RH is again de-energized. As tie-energization of the heater RH allows the bi-metal actuator 31 to cool, it can be seen that the switching assembly will alternate or oscillate between the first and second intermediate states to that engagement between contacts'45 and 46 is alternately made and broken, the heater RH being alternately energized and de-energized thereoby. Stated in another way, a given average power level will be applied to the heater RH, by a so-called hunting mode of operation, so as to maintain the actuator in a stable state or situation in which the generation of sparking impulses is inhibited but the solenoid valve is held open. If, during this operation; theflame is somehow extinguished, the bi-metal element will continue to cool even after the contact 46' is released since the complementary SCR, controlled by the flame rectification signal, will not produce energization of the heater RH through the SCR Q1. Accoridngly,.the bi-metal will continue to cool until the contacts 45 and 44 are disengaged to remove the short across the storage capacitor C1. At that time contacts 42 and 44 will remain engaged and cause igniting pulses to be generated as described above. If the resultant sparks produce ignition, the actuator 31 will again be heated and return to its intermediate state constitutingthe hunting mode between contacts 45 and 46. However, if ignition is not obtained the actuator 31 will continue to cool and proceed to the above described standby state requiring reset by a momentary interruption of power.

Should the SCR Q1 short or some other failure take place which would cause continued energization of the heater RH, independent of the flame-sensing circuitry, the actuator 31 will be caused by this continuous energization to proceed to an overload or final state in there is a manual resetting of the circuitry, either by replacing the fuse F1 or resetting an equivalent circuit breaker. Conversely, should the SCR Q1 circuit open or some other failure occur that prevents energization of the heater RH, the actuator 31 will proceed to the initial state shown in FIG. 1 and because of the open circuit, further operation can be instituted only by personal service of the system at the burner. Thus, the system shown is failsafe in the sense of preventing, under any conditions, fuel flow in the absence of flame.

In view of the foregoing, it may be seen that several objects of the present invention are achieved and other advantageous results have been attained.

Without departing from the scope of the invention, various changes could be made in the programmer of the type shown and disclosed so as to provide circuit functions other than those specifically described or in a different sequence than that described. For example, by eliminating the initial state bias on the leaf 33, the system would provide retries for ignition. In addition, the programmer could be mechanically coupled so as to directly control elements such as fuel supply valves or circuit breakers rather than controlling such elements electrically, as shown. Also, the functional action of the programmer need not be reversible as specifically shown; i.e., functional contacts could be made by the actuator in only one direction of travel. It should be understood, therefore, that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: 1. Apparatus for programming the sequence of operation of a burner which is provided with fuel through a valve, said apparatus comprising:

switching means including output means for providing a plurality of electrical outputs and an electrically energizable actuator means sequentially activatable through predetermined initial, intermediate and final states, with corresponding initial, intermediate and final outputs each operational in one of said states; said actuator comprising a thermally responsive means and a heat source therefor;

control circuit means for selectively controlling energization of said actuator in response to the said output made operational thereby; and

valve actuator means responsive to said electrically energizable actuator means to maintain the valve closed in said initial and final states and open in said intermediate state.

2. Apparatus according to claim 1 wherein said switching means comprises a plurality of contacts for providing said outputs.

3. Apparatus according to claim 2 wherein said thermally responsive means comprises a bi-metal element and said heat source comprises a resistive heater element electrically coupled to said control circuit means.

4. Apparatus according to claim 2 wherein said intermediate state is an unstable state that oscillates between first and second intermediate states that provide, respectively, a first intermediate output that energizes said heat source and a second intermediate output that de-energizes said heat source so as to produce oscillatory movement of said actuator.

5. Apparatus according to claim 4 wherein said control circuit means further comprises sensor means for sensing flame at the burner and for selectively controlling energization of said heat source in response to the operational output of said switching means.

6. Apparatus according to claim 5 including ignition means for igniting fuel provided to the burner, and wherein said switching means is further activatable through an ignition state that provides an ignition output that activates said ignition means, said ignition state being encountered by said switching means between said initial and intermediate states.

7. Apparatus according to claim 6 wherein said control circuit means comprises ignition control means for deactivating said ignition means with said switching means in said initial, intermediate or final states.

8. Apparatus according to claim ll wherein said valve actuator means comprises an electrical solenoid operatively coupled to said control circuit means.

9. Apparatus according to claim 1 wherein said control circuit means further comprises sensor means for sensing flame at the burner and for selectively controlling energization of said actuator in response to the operational output of said switching means.

l0.' Apparatus for programming the sequence of operation of a burner which is provided with fuel through an electrically operable valve and is provided also with electrical spark-generating and flame-sensing means, said apparatus comprising:

switching means including a plurality of contacts and an electrically energizable actuator which, when w energized, proceeds progressively in timed sequence through a succession of predetermined states, with corresponding contacts being operated in each state, the actuator returning back through said states when de-energized;

first circuit means responsive to the operation of said contacts in the initial state of said actuator for energizing said actuator the actuator being deenergized thereby when a second predetermined state is entered;

second circuit means responsive to the operation of said contacts in said second state for opening said valve and for generating spark producing impulses thereby to produce sparking at said burner; and circuit means responsive to the sensing of a flame at said burner for energizing said actuator independently of said first circuit means.

11. Apparatus as set forth in claim 10 in which said actuator comprises a bi-metal device and a heater thermally coupled to said bi-metal device.

12. Apparatus as set forth in claim 11 in which said bi-metal device carries one contact, said one contact engaging a first of the other contacts in said initial state and leaving said first contact in proceeding to subsequent states.

13. Apparatus as set forth in claim 12 in which subsequent ones of said other contacts are resiliently mounted and progression of said actuator causes previously engaged ones of said other contacts to be driven into engagement with successive ones of said other contacts.

14. Apparatus according to claim 13 wherein said first contact is retained in a resiliently biased position by said actuator in said initial state, said one contact and said other contacts are disposed such that said one contact leaves said first contact so as to de-energize said heater before engaging any of said other contacts; and said heater possesses suflicient thermal inertia to produce movement of said actuators one contact into engagement with one of said other contacts after deenergization of saidheater. 7

15. Apparatus as set forth in claim 10 wherein said second circuit means comprises a triggerable semiconductor device, a spark coil connected to said ignition electrodes, an energy storage capacitor, and means for triggering said semiconductor device when said capacitor is charged thereby to discharge said capacitor through said coil to produce igniting sparks at said electrodes.

16. Apparatus as set forth in claim wherein said flame responsive circuit comprises a trigger capacitor which is charged by flame conduction at one of said electrodes and a second semiconductor device for repetitively discharging said trigger capacitor to trigger said first semi conductor device.

17. Apparatus for programming the sequence of operation of a burner which is provided with fuel through an electrically operable valve and is provided alsowith electrical spark-generating and flame-sensing means, said apparatus comprising:

switching means including a plurality of contacts and an electrically energizable actuator which, when energized, proceedsthrough a succession of prede termined states with corresponding contacts being operated in each state; first circuit'means responsive to the operation of said contacts in the initial state of said actuator for energizing said actuator, the actuator being deenergized thereby when a second state is entered; second circuit means responsive to the operation of said contacts in said second state for opening said valve and for generating spark producing impulses thereby to produce sparking at said burner; circuit means responsive to the sensing of a flame at said burner for inhibiting the generation of spark producing impulses by said second circuit means and for energizing said actuator independently of said first circuit means; and further circuit means responsive to the operation of said contacts in' a subsequent state of said actuator for de-energizing said actuator independently of the operation of said flame responsive circuit whereby said actuator alternates between said subsequent state and a previous state when a flame has been established at said burner.

18. Control apparatus for use with a burner which is provided with fuel through an electrically controllable valve and is provided also with spark ignition and flame sensingelectrodes; said apparatus comprising:

switching means including a plurality of contacts, a

bi-metal actuator and a heater which, when energized, heats said actuator and causes said actuator discharge said capacitor through said coil to produce igniting sparks at said electrodes, said sparkgenerating circuit being interconnected with said contacts to be energized through said actuator heater when said actuator is in a second of said states, the current drawn by spark generation being insufficient to cause said actuator to proceed; and

means responsive to the presence of a flame at said burner for repetitively triggering said semiconductor device at a rate faster than that permitting charging of said energy storage capacitor thereby to draw sufficient current through said heater to cause said actuator to proceed.

19. Control apparatus for use with a burner which is provided with fuel through an electrically controllable valve and is provided also with spark ignition and flame-sensing electrodes; said apparatus comprising:

switching means including bi-metal actuator carrying an actuator contact, a plurality of other contacts mounted adjacent said actuator contact, and a heater which, when energized, heats said actuator and causes said actuator to proceed from an initial state through a succession of predetermined subsequent states, one of said other contacts being engaged by said actuator contact in said initial state and being disengaged in said subsequent states, the remaining other contacts being successively engaged electrically by said actuator contact in said subsequent states;

first circuit means interconnecting said one contact and said heater thereby to energize said heater in said first state;

spark-generating circuit including a triggerable semiconductor device, a spark coil connected to said ignition electrodes, an energystorage capacitor, and means for triggering said semiconductor device when said capacitor is charged thereby to' discharge said capacitor through said coil to produce igniting sparks at said electrodes, said sparkgenerating circuit being interconnected with a first one of said other contacts to be energized through said actuator heater when said actuator is in a second of said states, the current drawn through said heater by spark generation'being insutficient to cause said actuator to proceed;

means responsive to the presence of a flame at said burner for repetitively triggering said semiconductor device at a rate faster than that permitting charging of said energy storage capacitor thereby to draw sufficient current through said heater to cause said actuator to proceed; and

means interconnected with a further one of said other contacts for inhibiting triggering of said semiconductor device in a later one of said states, whereby, in the presence of flame at said burner, said actuator alternates between said later one of said states and the next proceeding one of said states.

20. Apparatus as set forth in claim 19 in which said apparatus is energized through a current overload protection device and in which the contact engaged in the last of said states is connected to draw sufficient current to operate said protection device.

21. Apparatus for programming the sequence of operation of a burner which is provided with fuel through a valve, said apparatus comprising:

sensor means for sensing the presence of flame at the burner;

switching means including output means for providing a plurality of electrical outputs and sequentially and reversibly activatable through predetermined initial, intermediate and final states, with corresponding initial, intermediate and final outputs each operational in one of said states;

power responsive actuator means for activating said switching means toward said initial state in response to power levels below a given level and toward said final state in response to power levels above said given level;

power supply means for supplying power to said actuator means and comprising control circuit means for regulating the level of power supplied thereto, said control circuit adapted to maintain said switching means in said intermediate state by providing said given power level only in response to the presence of flame at said burner as indicated by said sensor means; and

valve actuator means for maintaining the valve closed with said switching means in said initial and final states and open with said switching means in said intermediate state.

22. Apparatus according to claim 21 wherein said switching means comprises a plurality of contacts connected with said power supply means and said valve actuator means.

23. Apparatus according to claim 22 wherein said power responsive actuator means comprises a thermally responsive means and a heating means therefor electrically coupled to said control circuit means.

24. Apparatus according to claim 22 wherein said intermediate state comprises first and second intermediate states each of which provide outputs and wherein said control circuit means responds to said first intermediate state by providing a power level above said given level and responds to said second intermediate state by providing a power level below said given level thereby causing said switching means to oscillate between said first and second intermediate states.

25. Apparatus according to claim 22 including ignition means for igniting fuel provided to the burner, and wherein said switching means is further activatable through an ignition state that provides an ignition output that activates said ignition means, said ignition state being encountered by said switching means between said initial and intermediate states.

26. Apparatus according to claim 22 wherein said control circuit means comprises ignition control means for deactivating said ignition means with said switching means in said initial, intermediate or final states.

27. Apparatus according to claim 22 wherein said valve actuator means comprises an electrical solenoid operatively coupled to said control circuit means. 

1. Apparatus for programming the sequence of operation of a burner which is provided with fuel through a valve, said apparatus comprising: switching means including output meaNs for providing a plurality of electrical outputs and an electrically energizable actuator means sequentially activatable through predetermined initial, intermediate and final states, with corresponding initial, intermediate and final outputs each operational in one of said states; said actuator comprising a thermally responsive means and a heat source therefor; control circuit means for selectively controlling energization of said actuator in response to the said output made operational thereby; and valve actuator means responsive to said electrically energizable actuator means to maintain the valve closed in said initial and final states and open in said intermediate state.
 2. Apparatus according to claim 1 wherein said switching means comprises a plurality of contacts for providing said outputs.
 3. Apparatus according to claim 2 wherein said thermally responsive means comprises a bi-metal element and said heat source comprises a resistive heater element electrically coupled to said control circuit means.
 4. Apparatus according to claim 2 wherein said intermediate state is an unstable state that oscillates between first and second intermediate states that provide, respectively, a first intermediate output that energizes said heat source and a second intermediate output that de-energizes said heat source so as to produce oscillatory movement of said actuator.
 5. Apparatus according to claim 4 wherein said control circuit means further comprises sensor means for sensing flame at the burner and for selectively controlling energization of said heat source in response to the operational output of said switching means.
 6. Apparatus according to claim 5 including ignition means for igniting fuel provided to the burner, and wherein said switching means is further activatable through an ignition state that provides an ignition output that activates said ignition means, said ignition state being encountered by said switching means between said initial and intermediate states.
 7. Apparatus according to claim 6 wherein said control circuit means comprises ignition control means for deactivating said ignition means with said switching means in said initial, intermediate or final states.
 8. Apparatus according to claim 1 wherein said valve actuator means comprises an electrical solenoid operatively coupled to said control circuit means.
 9. Apparatus according to claim 1 wherein said control circuit means further comprises sensor means for sensing flame at the burner and for selectively controlling energization of said actuator in response to the operational output of said switching means.
 10. Apparatus for programming the sequence of operation of a burner which is provided with fuel through an electrically operable valve and is provided also with electrical spark-generating and flame-sensing means, said apparatus comprising: switching means including a plurality of contacts and an electrically energizable actuator which, when energized, proceeds progressively in timed sequence through a succession of predetermined states, with corresponding contacts being operated in each state, the actuator returning back through said states when de-energized; first circuit means responsive to the operation of said contacts in the initial state of said actuator for energizing said actuator the actuator being de-energized thereby when a second predetermined state is entered; second circuit means responsive to the operation of said contacts in said second state for opening said valve and for generating spark producing impulses thereby to produce sparking at said burner; and circuit means responsive to the sensing of a flame at said burner for energizing said actuator independently of said first circuit means.
 11. Apparatus as set forth in claim 10 in which said actuator comprises a bi-metal device and a heater thermally coupled to said bi-metal device.
 12. Apparatus as set forth in claim 11 in which said bi-metal device carries one contact, said one contact engaging a first of the other contacts in said initial state and leaving said first contact in proceeding to subsequent states.
 13. Apparatus as set forth in claim 12 in which subsequent ones of said other contacts are resiliently mounted and progression of said actuator causes previously engaged ones of said other contacts to be driven into engagement with successive ones of said other contacts.
 14. Apparatus according to claim 13 wherein said first contact is retained in a resiliently biased position by said actuator in said initial state, said one contact and said other contacts are disposed such that said one contact leaves said first contact so as to de-energize said heater before engaging any of said other contacts; and said heater possesses sufficient thermal inertia to produce movement of said actuator''s one contact into engagement with one of said other contacts after de-energization of said heater.
 15. Apparatus as set forth in claim 10 wherein said second circuit means comprises a triggerable semiconductor device, a spark coil connected to said ignition electrodes, an energy storage capacitor, and means for triggering said semiconductor device when said capacitor is charged thereby to discharge said capacitor through said coil to produce igniting sparks at said electrodes.
 16. Apparatus as set forth in claim 15 wherein said flame responsive circuit comprises a trigger capacitor which is charged by flame conduction at one of said electrodes and a second semiconductor device for repetitively discharging said trigger capacitor to trigger said first semi conductor device.
 17. Apparatus for programming the sequence of operation of a burner which is provided with fuel through an electrically operable valve and is provided also with electrical spark-generating and flame-sensing means, said apparatus comprising: switching means including a plurality of contacts and an electrically energizable actuator which, when energized, proceeds through a succession of predetermined states with corresponding contacts being operated in each state; first circuit means responsive to the operation of said contacts in the initial state of said actuator for energizing said actuator, the actuator being de-energized thereby when a second state is entered; second circuit means responsive to the operation of said contacts in said second state for opening said valve and for generating spark producing impulses thereby to produce sparking at said burner; circuit means responsive to the sensing of a flame at said burner for inhibiting the generation of spark producing impulses by said second circuit means and for energizing said actuator independently of said first circuit means; and further circuit means responsive to the operation of said contacts in a subsequent state of said actuator for de-energizing said actuator independently of the operation of said flame responsive circuit whereby said actuator alternates between said subsequent state and a previous state when a flame has been established at said burner.
 18. Control apparatus for use with a burner which is provided with fuel through an electrically controllable valve and is provided also with spark ignition and flame sensing electrodes; said apparatus comprising: switching means including a plurality of contacts, a bi-metal actuator and a heater which, when energized, heats said actuator and causes said actuator to proceed from an initial state through a succession of predetermined subsequent states, one of said contacts being engaged in said initial state and being disengaged in said subsequent states, the remaining contacts being successively engaged in said subsequent states; first circuit means interconnecting said one contact and said heater thereby to energize said heater in said first state; a spark-generating circuit including a triggerable semiconductor device, a spark coil connected to said ignition electrodes, an energy storage capacitor, and means for triggering said semiconductor device when said capacitor is charged thereby to discharge said capacitor through said coil to produce igniting sparks at said electrodes, said spark-generating circuit being interconnected with said contacts to be energized through said actuator heater when said actuator is in a second of said states, the current drawn by spark generation being insufficient to cause said actuator to proceed; and means responsive to the presence of a flame at said burner for repetitively triggering said semiconductor device at a rate faster than that permitting charging of said energy storage capacitor thereby to draw sufficient current through said heater to cause said actuator to proceed.
 19. Control apparatus for use with a burner which is provided with fuel through an electrically controllable valve and is provided also with spark ignition and flame-sensing electrodes; said apparatus comprising: switching means including bi-metal actuator carrying an actuator contact, a plurality of other contacts mounted adjacent said actuator contact, and a heater which, when energized, heats said actuator and causes said actuator to proceed from an initial state through a succession of predetermined subsequent states, one of said other contacts being engaged by said actuator contact in said initial state and being disengaged in said subsequent states, the remaining other contacts being successively engaged electrically by said actuator contact in said subsequent states; first circuit means interconnecting said one contact and said heater thereby to energize said heater in said first state; a spark-generating circuit including a triggerable semiconductor device, a spark coil connected to said ignition electrodes, an energy storage capacitor, and means for triggering said semiconductor device when said capacitor is charged thereby to discharge said capacitor through said coil to produce igniting sparks at said electrodes, said spark-generating circuit being interconnected with a first one of said other contacts to be energized through said actuator heater when said actuator is in a second of said states, the current drawn through said heater by spark generation being insufficient to cause said actuator to proceed; means responsive to the presence of a flame at said burner for repetitively triggering said semiconductor device at a rate faster than that permitting charging of said energy storage capacitor thereby to draw sufficient current through said heater to cause said actuator to proceed; and means interconnected with a further one of said other contacts for inhibiting triggering of said semiconductor device in a later one of said states, whereby, in the presence of flame at said burner, said actuator alternates between said later one of said states and the next proceeding one of said states.
 20. Apparatus as set forth in claim 19 in which said apparatus is energized through a current overload protection device and in which the contact engaged in the last of said states is connected to draw sufficient current to operate said protection device.
 21. Apparatus for programming the sequence of operation of a burner which is provided with fuel through a valve, said apparatus comprising: sensor means for sensing the presence of flame at the burner; switching means including output means for providing a plurality of electrical outputs and sequentially and reversibly activatable through predetermined initial, intermediate and final states, with corresponding initial, intermediate and final outputs each operational in one of said states; power responsive actuator means for activating said switching means toward said initial state in response to power levels below a given level and toward said final state in response to power levels above said given level; power supply means for supplying power to said actuator means and comprising control circuit means for regulating the level of power supplied thereto, said controL circuit adapted to maintain said switching means in said intermediate state by providing said given power level only in response to the presence of flame at said burner as indicated by said sensor means; and valve actuator means for maintaining the valve closed with said switching means in said initial and final states and open with said switching means in said intermediate state.
 22. Apparatus according to claim 21 wherein said switching means comprises a plurality of contacts connected with said power supply means and said valve actuator means.
 23. Apparatus according to claim 22 wherein said power responsive actuator means comprises a thermally responsive means and a heating means therefor electrically coupled to said control circuit means.
 24. Apparatus according to claim 22 wherein said intermediate state comprises first and second intermediate states each of which provide outputs and wherein said control circuit means responds to said first intermediate state by providing a power level above said given level and responds to said second intermediate state by providing a power level below said given level thereby causing said switching means to oscillate between said first and second intermediate states.
 25. Apparatus according to claim 22 including ignition means for igniting fuel provided to the burner, and wherein said switching means is further activatable through an ignition state that provides an ignition output that activates said ignition means, said ignition state being encountered by said switching means between said initial and intermediate states.
 26. Apparatus according to claim 22 wherein said control circuit means comprises ignition control means for deactivating said ignition means with said switching means in said initial, intermediate or final states.
 27. Apparatus according to claim 22 wherein said valve actuator means comprises an electrical solenoid operatively coupled to said control circuit means. 